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Flash Modin writes "Death Star style superlasers? Don't bet on it. High-power lasers currently in development appear to be nearing the theoretical laser intensity limit, according to new research set to be published in the journal Physical Review Letters. Ultra-high-energy laser fields can actually convert their light into matter as shown in the late '90s at the Stanford Linear Accelerator (SLAC). This process creates an 'avalanche-like electromagnetic cascade' (also known as sparking the vacuum) capable of destroying a laser field. Physicists thought it might be a problem for lasers eventually, but this work indicates the technology is much closer to its limit than researchers believed. A preprint is available here."

People using their imagination to go beyond the limits of current technology? Don't bet on it.

But seriously, anything with the firepower of the Death Star would probably be using high intensity anti-neutronium particle beams or something to that effect.
Reminds me of a Star Trek TNG episode where the Enterprise-D was threatened by a ship armed only with high power lasers -- the crew thought it was quaint of course.

Creating light from matter is rather ordinary in terms of physics, as can be seen in nuclear explosions

Or even running out of lighter fluid.

The SLAC experiment was just a singular event, but as lasers reach higher intensities the electric fields produced will increase as well and the team says that when they reach a critical intensity a cascade effect will occur as a result. The electron-positron pair is accelerated by the laser field itself at such high energies that they emit photons capable of spawning new pairs and continuing the process.

Maybe that's how the death star works? Besides, it isn't explicitly stated anywhere in the movies that the death star is a laser.

Also, they're not talking about a single laser, they're talking about colliding two laser beams.

Its true. We don't really know how the Death Star works. That's always been my biggest pet peeve with the "Star Wars" movies in that they really played up the "rebel vs. empire" theme (with a real bias towards the rebels IMO) and didn't focus on the technology or culture of that era. It really makes the documentary as a whole seem more like a fictional tale or something. Maybe Ken Burns will revisit that period of the galactic history and we'll get a more neutral viewpoint of the conflict.

In truth, it does always bother me how easy it seems to 'blow up' planets in fiction. If you think about it, the amount of energy required to blow up a planet would be equivalant to launching every bit of the earth into space, think about the amount of energy involved in just getting the tiny space shuttle into space, then think about doing that for mount everest, then think about doing that for mount everest about 10,000,000,000,000,000,000 times. That is how hard it is to blow up a planet (very roughly)

Well, let's see. Suppose we decide to accelerate an asteroid 100km in diameter using whatever long-term propulsion we can (nuke-powered VASIMIR, big solar sails, whatever) and use the well-known gravity assist that the planets can provide. If the asteroid has an average density of 4 g/cc, how fast would we have to get it going when it impacted earth to give enough energy to blow the planet apart?

Blow the planet apart = move all of its mass to escape velocity. Earth escape velocity is about 11.2 km/sec. 1kg moving at 11.2 km/sec has about 6.27e7 Joules of kinetic energy. Earth's mass is about 5.97e24 kg. (No, I didn't weigh it, but Google is my friend). So, to move all of the earth's mass away at a speed of 11.2 Km/sec would require (6.27e7 J/kg)*(5.97e24kg) = 3.75e32 Joules.

OK, this doesn't count the energy needed to break the rock up, but cut me some slack, this exercise is tuned to the accuracy standards of physicists, i.e., we're happy if we get it within a few orders of magnitude.

Back to our 100Km diameter billiard ball. It's mass is about 2.09e18kg. So, to get about 10^32 Joules of kinetic energy on target, it will have to be moving at about 10,000,000 m/sec. This is about 3% the speed of light.

This is surely overkill in that it's the energy needed to push all the earth's mass to escape velocity. Probably less than 1% of this energy would suffice to crack the planet into pieces. Would this count as blowing the earth up?

"Although the instant destruction and death of millions of residents and visitors to Alderaan was considered a major turning point in the Rebel movements popularity, Darth Vader was considered to have been acting within his remit by the wider Imperial corps. Also, they didn't want to get force-choked."

If you could track every atom of the lighter fluid, you'd see that there are as many atoms from the lighter fluid around after the combustion as before. In a nuclear explosion, there are fewer atoms around.

Also, they're not talking about a single laser, they're talking about colliding two laser beams.

They're aiming an electron beam at a laser - not quite the same thing as aiming two lasers at each other. Furthermore, the key part is not the e-beam, but the gamma-rays that come from the electron-photon collision, which then interact with the laser. The issue is that once you create one electron-positron pair from photons, you can get a cascade reaction where there are so many electrons/positrons floating around that you don't have a coherent laser field anymore.

In a nuclear explosion, there are fewer atoms around.
That depends entirely on the nuclear bomb. Fission weapons work by splitting uranium and/or plutonium into smaller atoms, at least doubling the number of atoms hanging around. Fusion weapons would result in fewer atoms, if they did not use fission triggers.

A certain amount of matter is converted into energy in every nuclear blast. That is why the equation E=MC^2 comes into play. It allows you to calculate the amount of M that was converted into E if you measure the amount of energy released in the blast.

Nuclear reactions don't conserve the number of subatomic particles. They conserve matter/energy, Baryon number (if there are any Baryons involved), and charge. Some also conserve 'spin'. As simple a reaction as neutron decay shows this. A neutron (1 particle) splits into a proton, an electron, and a neutrino (3 particles). That's beta decay. When the initial neutron is in a nucleus, the resulting proton stays there. The total mass of the three particles, plus the kinetic energy added to the electron and neu

If you could track every atom of the lighter fluid, you'd see that there are as many atoms from the lighter fluid around after the combustion as before. In a nuclear explosion, there are fewer atoms around.

There are more atoms around in fission, but that's not really important. However, there's as many electrons, protons, and neutrons as there were before. Fission doesn't destroy particles, it just releases nuclear binding energy.

Actually, from what I can see, the blaster, the death star's beam, the lightsaber and even the beam weapons on the clone wars gunship turrets seem to work on something other than "laser." They seem to operate on energized particles or energy that is transformed into a mass-like state. In the case of the death star, it would seem to explain why merging many beams from different angles could actually result in a single beam going in yet another angle.

In any case, you can see blaster bolts travel... they seem to fly at around arrow speed. The fact that they emit light leads people to think "laser" when in reality, you can't see a laser in most cases unless there is interference in the air. (BTW, did you ever notice that headlights seem to be less effective at night after a rainfall? That's because the roads are wet and more reflective... the light gets reflected away from your eyes and so you can't see the light bounce back to your eyes.)

Worse still, the term "laser sword" is actually used in Star Wars which doesn't help things at all. Young Anakin identifies Qui Gon as a Jedi because of his "laser sword." On one hand it is forgiveable because he's a kid, but on the other hand, he's a genius kid and should know better. In any case, lightsabers have a shadow (because of some sloppy film editing) but ostensibly because they are not lasers but an energy/matter transition state where energy is made to behave as matter. (Though only shown in games and cartoons, energy "bridges" are used to create temporary walkways using a technology similar to that used in lightsabers)

It's all fiction anyway, but it helps to try to understand the technology imagined in these fictions. The technologies imagined in SciFi are quite often candidate for implementation in our present or near future.

Here's my take. In SW, is an anti-matter particle beam. The glow you see is antimatter atoms reacting with the interstellar medium, which is less than total vacuum. Hence, you get some reactions (and losses) en route. This is what you see. It is also the only medium to generate that violent a reaction that quickly. A laser would simply heat it. And the problem with lasers if you have to be able to dissipate your inefficiencies. So if you have a

So if you have a 33% efficient laser of 1MW, you have to be able to dissipate 2MW yourself. This means everyone on the Death Star would cook, and it would blow itself up twice as fast as Alderan. (Assuming Alderan's the DS's thermal properties are the same, etc)

Well, thank goodness we just installed that thermal exhaust port up on the top layer then.

Burning lighter fluid is a chemical reaction, the same amount of matter exists before and after, it just exists in new compounds. Nuclear explosions actually destroy matter.

Seriously? Nuclear explosions don't destroy anything. They split atoms into smaller atoms (or merge two atoms into a larger atom with fusion) which releases energy held up in the atom itself. Matter is definitely not destroyed. The only way to "destroy" matter (turn matter into energy; you can't completely destroy it) is with anti-matter.

But it is energy that was stored in a either a chemical bond, or an electron state. Matter does not disappear, it is just electrons rearranging their orbits. If you count all the protons, neutrons and electrons before and after the chemical reaction, they're all still there.

Both nuclear and chemical reactions destroy matter, if you can call that destroying matter.

In a chemical reaction, electrons change states. In an exothermal chemical reaction, the energy of those electron states is lower than the energy of the electron states before the reaction, and energy is released in another form (photons, kinetic energy, etc.). If you count the neutrons, protons, and electrons, they're all still there. But mass has been lost, because the binding energy of the electrons counts in the mass of the molecule. (In the reaction, binding energy was lost and converted to another form. Energy is mass.) However, chemical binding energy is tiny compared to the energy in the rest mass of protons, neutrons, and electrons.

In a nuclear reaction (fission and fusion), the states of nucleons (neutrons and protons) also change. Again, if you count the neutrons, protons, and electrons, the same ones present before are present after. (Sometimes they change form, like n p + e.) But mass has been lost, because the binding energy between the nucleons counts in the mass of the atom. (In the reaction, binding energy was lost and converted to another form. Energy is mass.) Nuclear binding energy is still small compared to energy in rest mass, but it's a lot bigger than chemical binding energy.

People talk about "transforming mass into energy" in nuclear reactions, but they almost never say that it's actually much more mundane than that. You don't need nuclear reactions (or even chemical reactions): a sinning top, for example, has more mass than one that's standing still. Here [discovermagazine.com] is a somewhat known physicist talking about that, if you don't want to believe a random person on Slashdot.

True, but if you could actually measure the mass of the butane molecule with enough precision, you would find that it is more massive than the constituent atoms alone. This extra mass (m=E/c^2) is actually due to the potential energy stored in the bonds.

GP is correct, the chemical and nuclear reactions are completely analogous, in each there is a change in mass due to a change in bond energies, but this change is much smaller in magnitude in chemical reactions.

Chemical bonds are matter, just as much as nuclear bonds are. It's a marvel of the universe.I think you'll also find that, seen from your immediate surroundings, you gain mass as you fall off the building and your velocity increases. Though you'll also briefly experience weightlessness, so I suppose it's not wrong to say that you lose weight.

No, none of the matter was converted to energy. Chemical bonds were broken apart, and the energy that comprised them was dissipated as heat and light. Not one proton, neutron or electron was destroyed in the process.

Energy is matter, matter is energy, it must be in one form or the other

Matter is a different thing than mass, and much more difficult to define. Energy is mass and mass is energy, and it's not that it must be one or the other, they are literally the same thing. Matter is generally things we consider to have rest mass, which isn't the same as mass. Rest mass is a form of energy (and thus mass, duh).

What you said about butane is right; it's heavier. It's not that there's more matter, but there is more mas

They don't "stop for a fraction of a second", they merely reflect off the mirrors... try using the patented CSI "infinite magnification of a digital image" technique next time to zoom in close enough to see the mirrors.

That part I wasn't waiting for, but actually this light-into-matter might be exactly what you want. Light is messy for this, but if you can have your lasers converge and convert into a stream of antimatter particles, things would surely get more interesting.

The one thing this does bugger up big time, though -- I spent HOURS trying to work out how bright headlights would need to be to propel a car backwards. The headlights would be so totally over this limit that you'd end up smashing the headlight covers in

At the speed of light, the car would have zero length but infinite mass. At infinite mass, it would convert itself into a black hole. Since a black hole won't allow light to escape, the light would eventually shine back on you. Since the amount of power needed in a headlight to move a typical car (plus the batteries needed to power said headlight) would be in the trillions of watts, you would be totally atomized as you were being crushed by the gravity.

Everything that can be invented has been invented.
The telephone has too many shortcomings to be seriously considered as a means of communication.
640k ought to be enough for anybody.
Turns out nobody can ever predict the future of technology (except maybe Orwell, but no one wants to admit that).
Just because we can't think of any way to break this "theoretical limit" doesn't mean it can't be broken. I'm sure at one time they said it was impossible to go faster than sound.

Before 1947, it was believed that the speed of sound represented a physical barrier for aircraft and pilots. As airplanes approach the speed of sound, a shock wave forms and the aircraft encounters sharply increased drag, violent shaking, loss of lift, and loss of control. In attempting to break the barrier, several planes went out of control and crashed, injuring many pilots and killing some. The barrier was eventually shown to be mythical, however, when Chuck Yeager surpassed the speed of sound in

Its been suggested some planes in WWII, in dives, were actually breaking/transitioning the sound barrier. This is why many planes never pulled out of their dive and crashed into the ground. The reason being, not enough control surface to function with the shock waves (compressibility) to allow for maneuvering to avoid their fate. This was, in fact, a fate repeated by many test pilots who attempted to break the sound barrier. It wasn't until the flying control surface was created that the problem was licked.

Unfortunately, that opening paragraph is horribly written. The rest of the entry is better, and gives an accurate though terse description of the problem. Before the 1940s, many aeronautical engineers believed -- quite rightly, givem the technology of the day -- that they couldn't design a plane that would hold together while passing Mach 1. Nobody ever claimed that it was physically impossible to fly faster than sound, and of course such a claim would have been absurd given that there were plenty of examples of things that did just that (e.g. bullets.) Serious attempts to build a supersonic airplane began in the 1930s, and by the start of WW2 everyone working in the high-performance aircraft field knew it was possible, they just didn't know exactly how to do it.

In short, it was an engineering problem, not a scientific one. This is completely different from limitations which are founded, as far as we can tell, not in the state of technology but in the laws of nature.

If out current understanding of the limiting natural laws turns out to be wrong, great -- I'd love to see a Death Star just as much as any nerd would. But don't bet on it. The fact that the X-1 flew no more means that we'll someday have faster-than-light starships with planet-destroying laser weapons than the existence of the internal combustion engine implies that perpetual motion machines are right around the corner.

In a report published this month by the journal Physical Review Letters, 20 physicists from four research institutions disclosed that they had created two tiny specks of matter -- an electron and its antimatter counterpart, a positron -- by colliding two ultrapowerful beams of radiation.

As for this being new...

The possibility of doing something like this was suggested in 1934 by two American physicists, Dr. Gregory Breit and Dr. John A. Wheeler.

Energy converts to matter, and matter to energy, all the time. Check out Feynman diagrams [wikipedia.org] for many examples. Particle colliders are machines built for the purpose of converting energy into matter. When particles collide, some of their energy converts to various forms of matter.

This is a common misconception. No, the particles that result from collisions were not already there. The top quark was created from a collisions of particles that did not contain a top quark. The same is true of bottom quarks, strange quarks, and charm quarks. The particles come from the energy of the colliding particles. That's why the energy of the collisions determines the maximum amount of mass of the particles the collider can create.

Just think about it for a few seconds. If new particles could not result, how can we make new types of quarks and antimatter? When we collide electrons and positrons, how could other types of particles possibly result?

Einstein disagrees with you. He says that energy and matter and interconvert, according to E=mc^2. This is exactly how particle colliders work. The LHC pumps lots of energy into hadrons and smashes them together, converting some of the energy into many different particles. We hope to be able to see Higgs bosons that are created in this way. Because they are proposed to be massive particles, lots of energy is needed to create them.

What E=mc^2 actually means is that energy includes a term involving mass. If you wanted to count up all the energy in something, you have to include some that is due to mass-energy. So suppose you want to get a bunch of kinetic energy to blow something up. One way to do that is to convert some chemical potential energy into kinetic energy; that's how dynamite works. Einstein is saying that there's another way: by converting some mass energy into kinetic energy; that's how a nuclear bomb works.

Creating light from matter is rather ordinary in terms of physics, as can be seen in nuclear explosions. But the SLAC experiment was the first to produce the opposite, and while the effect had been expected for some 50 years, the equipment hadn't existed to test it experimentally. It is known amongst physicists as creating "spark in a vacuum." When the electromagnetic field has enough energy, light becomes matter as a positron-electron pair is produced.

An atom is a collection of matter, which would be sort of a second step. Light is just energy, typically we are concerned with 'visible' light (or something close thereto) with Lasers and use the term Maser for microwaves for example, but the principles are the same. e=(gamma) m*c^2 and all that. Enough energy and you can make whatever sorts of matter you want. Normally with big colliders we are interested in producing some matter no one has seen before, so the more mondane making regular protons, elect

Ow! I just got hit with an electron! Ow! A positron! Mommmmmm! Make him stop! He's throwing electrons at me!

I suspect electrons and positrons don't exactly make audible "splat" noises when they hit something... But then, explosions in space are actually silent, and big yellow flames don't normally occur in a vacuum either.

I have not seen anyone answer you. Twenty years ago when I studies such things, 1% for something like a HeNe laser was good. I hear the National Ignition Facility lasers are good to maybe 4%. The quantum efficiency of a laser diode might be as high as 60%.
You have a couple of considerations. In an optically pumped laser, you have the efficiency of creating the pump photons. These put the lasing medium in an excited state which happens as some fraction less than 100%. Lastly, the excited state medium can e

Henchman: "Professor, I've increased the laser's power to a new incredible limit, and something remarkable has happened. It is creating new matter! I can tune the beam to create any matter in any configuration we need!"Professor: "Darn. We needed a big laser. Oh well, throw it all out, that was a dead end."

Isn't the fact the electron/positron pairs can be created in a vacuum by a strong enough electromagnetic field pretty interesting Physics in and of itself? What goes around comes around -- every day we get closer to resurrecting the theory of the luminiferous aether... (Yeah, I know... energy in a vacuum is not exactly the same thing.)

...what about PHASERS? What about other materials that get lased? Whenever I hear something about "we're reaching the end of [insert technology here]'s abilities" I always take it with a grain of salt. Sure, with current techniques and materials we are reaching the end of the power curve, but we're certainly not at the dead end for the technology. Or, maybe we are, but there will certainly be something that comes along to supplant it. It's not like oil where there is a finite supply of the stuff. How m

The researchers at the SLAC need to recheck their results, because Andy Schlafly, Conservapedia founder and a Eagle Forum "University" instructor has noted that E=mc^2 is a liberal plot [talkingpointsmemo.com].